As an open architecture of a small cell is modularized, not only a baseband unit and a radio frequency unit are separately used as independent modules, but also a filter in the radio frequency unit is designed as an independent structure. A specific quantity of filters may be selected according to different frequency bands and freely combined. A configuration is relatively flexible.
As shown in FIG. 1, a currently provided filter and antenna feeder connector are integrated into one body. A through hole is disposed in a box body. The filter is installed inside the box body. The antenna feeder connector penetrates the box body through the through hole in the box body. Then the antenna feeder connector is fastened by using a hex nut in cooperation with a waterproof rubber pad and a locking washer. As shown in FIG. 1, the filter and the antenna feeder connector are integrated into one body, and a size of the through hole in the box body exactly matches the antenna feeder connector, to meet a requirement of waterproofing and high isolation. During installation, the antenna feeder connector is aligned with a position of the through hole, and the filter is pushed forward and installed inside the box body, so that the antenna feeder connector penetrates the through hole. In this installation manner, a transmit port and a receive port of the filter and a printed circuit board (PCB) installed at the bottom of the box body cannot implement blind-mate. In addition, because installation needs to be implemented by pushing the filter forward, more interior space of the box body is required. In addition, the hex nut fastening the antenna feeder connector tends to apply a counter force to the antenna feeder connector. Consequently, the nut becomes loose, grounding fails, and intermodulation is hindered.